The recent introduction of buspirone having a selectivity for 5-HT.sub.1A receptors, as an effective anxiolytic agent U.S. Pat. No. 3,717,634), into the U.S. marketplace has stimulated interest in development of second-generation anxiolytic agents.
Furthermore, in clinical trials, gepirone and ipsapirone were found to be potent anxiolytic drugs. Since both drugs--gepirone and ipsapirone--possess a higher degree of selectivity for 5-HT.sub.1A receptors than buspirone, the clinical data supports the notion that anxiety mechanisms can be directly modulated by 5-HT.sub.1A receptor drug interactions.
In addition to treatment of anxiety, 5-HT.sub.1A agonists such as gepirone are now being examined for their mixed activity as anxiolytic antidepressant agents. The therapeutic potential of 5-HT.sub.1A agonists in the treatment of multi-CNS disorders was recently extended to the development of antipsychotic anxiolytic agents represented by MDL-72832 and KS-9172 (Br. J. Pharmacol., 90, 273P, 1987), the latter being under development as an antipsychotic agent (Scrip No. 1265, Dec. 11, 1987). This class of compounds demonstrated high affinity for both the 5-HT.sub.1A and D.sub.2 receptor binding sites.